Multiple effect still with thermocompression of vapors



R. OHENSZEY 2,440,173

MULTIPLE EFFECT STILL WITH THERMOCOMPRESSION OF VAPORS April 2o, 194s.

Filed June 15. 1942 2 Sheets-Sheet 1 April 20, 1948. R. o. HENszl-:Y

MULTIPLE EFFECT STILL WITH THERMOCOMPRESSION OF VAPORS Filed June 15,1942 2 Sheets-Sheet 2 w MN U QN wmmww Qwkm,

Patented Apr. 20, 1948 MULTIPLE EFFECT STILL WITH THERMO- COMPRESSION OFVAPORS Roy 0. Henszey. Oconomowoc. Wis. Application June 15, 1942.Serial No. 447,170

` zo claims. (c1. 2oz- 114) 1 i This invention yrelates to improvementsin stills and methods of distillation or concentration.

For simplicity, the invention will be explained with reference to astill for purifying sea water.

'I'he major object of the invention is to provide for repeated re-use ofheat to enhance the emciency. More particularly, I propose to conductevaporation at a succession of pressure and temperature levels,repeatedly returning heat from a lower heat level to a higher heat levelso that the same heat will be re-used in theV cycle of evaporation. Bythe present invention I seek td increasethe heat eiilciency of a threeeffect still more than fifty percent as compared with devices previouslyknown for this purpose.

It is a further object of the invention to provide a still which isuseful for military purposes in that it is exceptionally compact andself-contained, radiates a minimum of heat 'such as might affect infrared detecting apparatus; and one which avoids the venting of any visiblejet of steam such as might be detectable visually.

While the device has been referred to as a still, it is obviously alsoeffective as an evaporator or a concentrator,` and is therefore usefulfor a variety of purposes other than that specifically described by wayof exemplication. Other objects and uses of the invention will beapparent to those skilled in the art upon study of the followingdisclosure.

In the drawings:

Fig. 1 is a view illustrating diagrammatically in perspective anapparatus embodying the invention, portions of the apparatus beingbroken away to expose in section the interior constr-uction.

Fig. 2 is a view in transverse section through one of the calandrias orstills and through certain other associated parts.

Fig. 3 is a fragmentary cross section through a, portion of the thirdeffect calandria.

Like parts are identified by the same reference characters throughoutthe several views.

The entire apparatus is so compact as to be readily portable. In oneself-contained unit it includes the furnace or boiler 5 with a boilerfeed tank or hot well 6 and a steam :let compressor 1 operated by steamcarried to it from the boiler through pipe 8. There are also severalsets of heat exchangers performing different functions as willhereinafter be described. The steam jet compressor 1 maintains'thedesired sequence of vapor pressures in the successive sets of apparatus,while the desired movement of liquid is controlled by pumps and traps.

Sea water lifted by pump 9 through the sea water inlet pipe I0 isdelivered from the pump through pipe Il through the tubesn o1' a.condenser l2. This condenser is a heat exchanger comprising a jacket l5with headers near its ends connected by tubes I4 through which the seawater passes. The water leaves the condenser |2 through pipe I5 which isequipped with a spring loaded valve I6 through which a part of the seawater may be returned through pipe I1 to the sea.

For maximum emciency of operation some of the returned sea water may berecirculated through pipe I8 back to the inlet Il). It may also, ifdesired, be passed through the radiator I9 through which air may bedrawn by fan 2D for cooling purposes. A thermostatic valve at 2l mayapportion to pipe I0 the sea water and the recirculated water tomaintain the temperature of water admitted to the condensersubstantially constant. The condenser may be then designed to handle thehottest water which will ever be required to be used in the apparatus,and the water actually used may be maintained at the temperature forwhich the condenser was designed, thus making for maximum emciency. Thistemperature control and recirculation is, however, an optional feature.

The loading valve I6 causes a portion of the sea water pumped throughthe condenser to pass upwardly from pipe I5 through pipe 23 to a heater25. The sea water will already have acquired some heat in the condenserl2. yThe heater 23 lis a heat exchanging device similar ln design to thecondenser having a jacket 26 provided adjacent its ends with headersconnected by pipes 21 through which thesea water passes. The jacketspace of the heater 25 communicates freely with the jacket space of thecondenser l2 so that the same vapors may circulate through both jackets,as will hereinafter be explained;

In passing through the jacket of the heater 25, the sea water will beheated to approximately the temperature of the vapors in the heater. Thewarmed sea Water will leave the heater through pipe 28, going to thebottom of a heater 30, preferably of a type providing for a plurality ofpasses of the sea water through the heating fluids therein. From the topof the heater 30 the sea water is returned through pipe 3l to the bottomof another similar heater 32. (See Fig. 2.)

From heater 32. the sea water is delivered 3 through pipe 35 into thefirst effect still A, construction of which is best illustrated in Fig.2.

There is a Jacket 38 which provides a sea water reservoir 31 in whichthe Water admitted through pipe 35 is maintained at a constant level bya float valve. Above this there is a vapor collecting dome at 39. Inreferring to a dome I use the -word generically to indicate any vaporcollecting chamber or passage.

The jacket surrounds the upper end of a c alandria casing 40 having aheader 4I. To the space below the header leads a large pipe 42 openingdownwardly from the sea water .space 31 of Jacket 36. From the headernumerous pipes 43 lead upwardly and open through the top of thecalandria casing 40. Hot vapor and gases supplied to the interior of thecalandria casing by means hereinafter to be described, evaporate waterfrom the sea water which is exposed to the heat in the pipes 43. The seawater has already been heated above its atmospheric boiling point in itspassage through the condenser and the several heaters already described,and a substantial part of the water admitted by the float valve willflash into steam immediately upon entering the Jacket. Another part ofits water component is readily evaporated in the calandria and the vaporescapes through the upper ends of the tubes 43 into the vapor dome 38.

.Ebullition may be extremely rapid, with the result that most or all ofthe liquid in the tubes 43 will be in rapid upward circulation and willbe carried out of the upper ends of the tubes. A canopy 44 catches suchliquid and returns it downwardly over the outside of the casing and backinto the pool of sea water collected in the well at 81. 'I'he vapor,freed from the majority of its entrained water, passes through aforaminous plate 45, which so distributesthe flow as to preclude anyhigh velocity, localized current from entraining and lifting water.

From the dome the vapor may pass tangentially into a separator 41 Withinthe cylindrical interior of which the vapor whirls to rid itselfcentrfugally of entrained water. The foraminous wall at 48 has an offsetmargin at 48' to skim off the water which is thrown to the out- Some ofthe vapor will be condensed in the heater 32 by delivery of heat throughthe walls of the pipes to the incoming sea water therein. The condensateand the vapor .will be forced by pressure differentials established ashereinafter explained, to pass outwardly from the bottom of heater 32through pipe 55 into the vapor space of the calandria 48 of still B.

In all respects previously described, the second still B is identicalwith the first. Its calandria casing 40 houses tubes 43 exactly as shownin Fig. 2. These tubes contain the partially concentrated brinedelivered into the reservoir of its jacket 36 through the pipe 50 fromthe first effect. Surrounding the tubes of the second effect calandriais the condensate and vapor admitted to the casing 40 from the heater.32. The condensate and vapor will now give off heat to the brine in thetubes for further evaporation in the second still to further concentratethe brine and to release additional vapor into the dome at the top ofthe second effect still B.

Freed of gaseous entrained brine in the manner previously described, thevapor from the second effect B will pass through pipe 56 into the jacketspace of heater 30 about the tubes through 'which the sea water ispassing enroute to the first effect. Passing downwardly through thevjacket of heater 30 the vapors, and such further condensate as may becondensed in the heater 30, are delivered through the pipe 51 to thejacket space within the casing 40 of the calandria oi' the third effect.Meantime the further concentrated brine in the reservoir of the secondeffect side of the whirling mass of vapor and the water is thereupondelivered back through the drain vent 49 into the reservoir in thecalandria jacket. 'I'he wall 48 may be reformed adjacent its openings,as shown in Fig. 2, to facilitate return to the vaporV space of vaporsand gases which have passed with the water behind the Wall.

The sea water has now received ilrst step concentration and willhereinafter be called brine. It is necessary te trace the movement bothof the brine and the vapors removed therefrom into the successiveeffects B and C.

The brine which remains in the reservoir 31 leaves the reservoir throughpipe 50 and enters the corresponding reservoir of the second effect Bthrough a oat controlled valve, the pipe 50 corresponding to pipe 35 inFig. 2. Since the pressure is lower in still B than in still A, some ofthe water of the brine will flash into vapor immediately upon enteringthe reservoir oi' still B.

Meantime the vapor, freed of all brine, has passed from the separatorthrough its axial outlet pipe 52 into the upper jacket space of theheater 32 (Fig. 1 and Fig. 2). The vapors pass downwardly through theheater 32, giving orf heat to the sea water which has already beenpartially heated and is traversing the pipes 53 of heater 32 in themanner previously described.

B is delivered. through pipe 58 tothe Jacket 36 of the third effect cwhere the float valve 59 maintains at constant level the brine in thereservoir 31. In the third effect C the brine'is brought to maximumconcentration (so far as the present disclosure is concerned) by flashat the reduced pressure and by further evaporation in the tubes 43 andthe extremely concentrated brine is removed at a predetermined ratethrough pipe 60 and discharged to waste by a pump 3|.

Obviously, the rate at which the pump is operated will determine notmerely the rate at which brine is withdrawn from the third effect C, butalso the rate at which brine is Withdrawn from the second and firsteffects B and A, and the rate at which sea water is admitted to thefirst effect A, all of these devices being maintained at constant levelby float valves which make them interdependent so that a reduction oflevel in the third effect C will be communicated to the precedingeffects.

Meantime the final extraction of vapor from the concentrated brinepasses from `the third effect C to its separator 41 and through theaxial outlet pipe 62 thereof into a duct 63 which leads to theinter-communicating jackets 26 and I3 of the heater 25 and condenser I2respectively. The vapor will first give up its heat to the slightlywarmed sea water in the tubes of the heater 25, and will thereupon giveup heat to the coldest sea water in the tubes of the condenser I2.

Condensate has formed in the casing 48 of the calandria of the firsteffect A. Such condensate leaves the first effect through pipe 64 andthe drain valve trap 65 and is led thence through pipe 66 into theheater 32 where it joinsv such liquid as' has been condensed in theheater from the vapors formed in the first effect still. A substantialpart of the hot condensate may flash into steam in the vapor space ofthe heater due to the considerably reduced pressure in the heater. Someof the vapor thus produced will be recondensed in the heater by givingoi! heaty to the sea water traversing the heater tubes. All condensate,vapor, and gas passes as previously described, through pipe 55 into thecasing of the second effect calandria.4 Here again, the condensate isremoved through a pipe 54 and a drain valve or trap 65 from whichanother pipe 86. identical with that previously described, leads intothe jacket space of the heater 30 where further flash evaporation andrecondensation occur.

Thus, through the pipe 51 from the Jacket space of heater 3|), all ofthe condensate and vapor formed in the first two effects and in theheaters 32 and 30, passes into the jacket space in the calandria 40 ofthe third effect still C. A similar discharge pipe 84 leads through asimilar drain valve or float valve trap 55.

From the trap 65 it is possible to deliver the condensate upwardly intothe condenser I2, but because the condensate is at its boiling pointvapor lock is apt to occur, and I prefer, therefore, not to elevate thehot liquid. Accordingly, pipe 68 is led from trap 65 to a condensatecooler 90 from the top of which a pipe 9| leads all vapor upwardly intocondenser i2. Condensate accumulated in the condenser flows back to thejacket of the condenser cooler 90 through pipe 92. From the bottom ofcondenser cooler 90 pipe 69 leads to a pump 10 which discharges thedistilled condensate through a flow indicator 1| and discharge pipe 12to the point of yuse. The flow indicator 1| may be made to offersufficient resistance to ilow to assure the by-passing through pipe 13of sumcient quantities of distilled water to supply the hot water in thefeed water tank 6 for the boiler 5, subject to the control of floatvalve 14 therein.

In the cooler the condensate is rapidly cooled by a coil 93 of anydesired capacity, which is supplied with the coldest water available.This may conveniently'be done by connecting the coil 'as a by-passacross the pump 9 which circulates the sea water through the apparatus.

In every such operation there are certain uncondensable gases to bedisposed of. In the assumed illustration these uncondensable gasesconsist primarily of air dissolved in the sea water. I dispose of these,and in addition, create the pressure differentials required for theoperation of the device, by means of the steam iet compressor 1. Thiscompressor has an inlet pipe 15 leading from the inter-communicatingjackets 26 and I3 of heater 25 and condenser I2' respectively, asclearly shown in Fig. 2. The steam jetdeveloped by the compressor 1 notonly produces a pressure slightly above atmospheric in the ilrst effectcalandria, but also draws a considerable vacuum in the jackets 26 andI3. This extracts from these jackets all remaining vapor and gas,whether condensable or non-condensable. 'Ihis vapor and gas is deliveredwith the steam at the same pressure and temperature into the steam spaceof the first effect calandria. Being at the same pressure andtemperature as the steam, the vapors and gases thus delivered into thissteam space give off their heat tothe Water or partially concentratedbrine in the tubes I3 of the first effect calandria.

Since the final effect is operated at subatmospheric pressures, it isnecessary to use some sort of a pump for venting non-condensable gases.In order to vent such gases. it is also necessary to withdrawsubstantial quantities of vapor, much of the heat energy of which could`not be sal-i vaged if it were discharged with the non-condensable gasesat this point of the system.

, In actual practice, the amount of steam required to vent thenon-condensable gases may be of the order of 10% lof all the steamrequired to operate the entire apparatus. Hence very considerableeconomies are effected by using the steam jet compressor which returnsnot only the steam used therein but also the non-condensable gases andthe relatively high volume oi vapor entrained therewith to the firsteffect where the vapor may be reused to deliver off its heat to theheated fluid in the first effect. The

-amount of vapor, so returned has heat energy usable in the first effectwhich more than justifies the amount of energy used in the compressor.Use of theV salvaged heat successively in the second and third effectsbrings about further substantial economies.

The purging of the non-condensable gases from all effects is thusaccomplished in one operation as an incident to these other advantages.In the heating fluid space of the rst effect, the non-condensable gasesare at superatmospheric pressure and, the steam and vapor beingsubstantially all condensed on its path through the heating fluid space,the non-condensable gases reach the point of discharge with very littlesteam or vapor mixed therewith.

Near the top of the rst effect calandria is aV baille 16 which need notbe duplicated in the other effects. This baille causes gases to follow apath upon which condensable gases have a chance to condense. As theuncondensed gases rise above the baffle they are vented at 11 through acondenser coil 18 which encircles the upper end of jacket 40 in the pathof the canopy 44. This assists in reducing the temperature of the gases,and the cooled gases and such condensate as may be moving therewith movethrough pipe 19 to a' iloat valve trap at 80 from which a pipe 8|returns the condensatezto the jacket of heater 32 while a pipe 82 leadsthe remaining gases to the hot well or feed Water tank 6. This tank isvented 'at 83. In it a final condensation of any remaining condensablegas is achieved while the air or other gas absolutely non-condensable escapes to the atmosphere. Meantime any heat remaining in thenon-condensable gas has been imparted to the feed water and the gaswhich escapes is virtually cooled to atmospheric temperature and isinvisible.

It is not essential to vent the air through the hot well if a moreefficient vapor vent condenser is employed, as indicated at 95. Thiscondenser contains a coil 9S (Fig. 2) which is exposed in condenser tothe sea water passing through pipe 35 toward-the first still.Condensation is handled by the same trap shown at 8|). It is notnecessary that both of these condensing arrangements be used. Either-maybe dispensed with. However, if condenser 95 is omitted, it is desirablethat the gases be vented below water level in the hot well so that noremaining plume of steam will betray the presence of the apparatus whenit is used for military purposes.

The steam compressor furnishes the pressure differential which assuresthe eicient and effective operation of the `device as described.

While the exact gures will vary in different inpound to 1 pound gauge,while the condenser jacket and heater 25 may be at a sub-atmos-Y phericpressure maintained to a vacuum equivalent to that produced by inches ofmercury.

This vacuum in the condenser i2 and the heater is likewise communicatedinto the third effect dome. The effect of this amount of vacuum in thethird effect dome acts to produce a somewhat lesser degree of vacuum inthe second effect dome and the third effect calandria amounting, in theassumed case, to approximately 14 inches of vacuum (Hg).

This in turn corresponds to a vacuum in the first effect dome and thesecond effect calandria of approximately 9 inches (Hg). It is because ofthe progressive reduction of pressure in the successive stills thatvapor may be successively evaporated in the successive stills atprogressively lower temperatures, the heat meantime having beendelivered up to the incoming sea water to raise it to the point where itwill evaporate at the maximum pressure existing in the first effect.

Fig. 3 illustrates how'non-condensable gases may be discharged from thetops of the vapor spaces of the second and third effect calandria. Inthis instance the gases are vented through a small duct 84 and ventfitting 85 into the vapor space 38 which, as above explained, is atlower pressure. The non-condensa'ble gases from the calandria vaporspace of the second effect can either be vented into the vapor space inthe dome of the second effect or into the vapor space of the dome of thethird effect. In any event, all non-condensable gases from the secondand third effects will ultimately be passed back through the compressorto the first effect, from which they will be discharged atsuper-atmospheric pressure. In the meantime all water vapor which hasnot been condensed in the condenser will be recompressed and used againwith the boiler steam. The heat of such vapor, as well as the heat ofthe non-condensable gases, is saved either in the 'brine of the firsteffect or in the boiler feed water.

With the device set up as described, a given weight of boiler steam willevaporate a nearly equal quantity of water from the brine in the firsteffect. The vapor from the first effect will, in turn, evaporate anearly equal weight of water from the brine in the second effect, whilethe vapor from the second effect will evaporate a nearly equal quantityof water from the brine in the third effect. If the quantities .were allexactly normal, one pound of boiler steam would thus evaporate threepounds of water in the successive effects.

By operating with a steam pressure not too high above atmospheric in thefirst calandria, and by maintaining a vacuum in the condenser which isnot too great, and at the same time by generating boiler steam at highpressure for use in the steam jet compressor, I am able to com- .pressand use in the first calandria more than half. of the vapor delivered tothe condenser. 'I'his reuses more than 50% of the quantity ofheat-originally delivered by the boiler and results in a very high heatefficiency. In practice my three effect evaporator has yielded more thanfour vpounds of distilled water per pound of steam used;

This high efficiency results in part from the fact that heat is passedfrom low heat levels back to high heat levels. fect by passing part ofthe heat in the vapor in This is done in the first ef-` the condenserback to the first calandria by compressing it from a vacuum in thecondenser to super-atmospheric pressure in the first calandria.Similarly in the successive effects, I reuse the heat in each stage byoperating at progressively decreasing pressures.

While no motors have been shown to operate the various pumps, it will beunderstood that any source of power may be used. Ii' steam engines areemployed, operated from boiler l, the used steam may be vented throughthe hot well 8. Likewise, if internal combustion engines are used, theheat developed in the jackets of such engines may be delivered to thehot well by circulating through the jackets the water of the hot well.In any case, whether the water in the hot well is heated by the gasesvented thereto through pipe 82, or whether the water in the hot well isheated by some extraneous means not constituting any part' of thepresent invention, I may desire to use the heat of the water in the hotwell to assist the functioning of the stills. One convenient way ofdoing this is to return such water through pipe 81 subject to thecontrol of any desired type of valve (such as that shown at 88) to theinlet pipe 55 which leads into the heating space of the calandria of thesecond effect B. The water in the hot well is distilled water and, uponbeing thus returned, it will commingle with other distilled waterto-heat the concentrates in the second still B, ultimately returning tothe condensate cooler and being pumped from the condensate cooler bymeans of pipe 89 and pump 10.

Reference has already been made to the effect of the steam jet pump 1 inestablishing superatmospheric pressure in the heating space of thecalandria of the first effect and a sub-atmospheric pressure in thecondenser jacket. Condensation in the condenser, as well as thecontinuous with drawal of condensate from such jacket by means of pipe69 and pump 10, assists in maintaining this pressure differential whichis relied upon to maintain the flow of condensate from the severalheaters 32 and 30 and the several stills A, B and C to the condenser orcondensate cooler.

I claim:

l. An evaporator comprising the combination with a calandria having aheating fluid passage and a heated fluidA passage, and means forcollecting vapor from the last mentioned passage, of a boiler fordeveloping steam pressure and provided with a hot well, a steam Jet pumphaving its outlet connected to the heating fluid passage of thecalandria and having an inlet connected to said boiler and a secondinlet communicating with said vapor collecting means, means forcondensing a portion of such vapor between the vapor collecting meansand the second inlet of said pump, said pump being adapted tore-compress uncondensed vapor and deliver it to the heating fluidpassage of said calandria, and means for venting from the heating fluidpassage of said calandria gases remaining uncondensed therein, saidventing means extending into the hot well below the level of the watertherein.

2. In a device of the character described, the combination with a boilerfor developing steam under pressure and a steam jet pump having oneinlet connected with the boiler and having a second inlet for fluid tobe pumped and having an outlet. of a series of at least threeevaporators each comprising a calandria having a first passage forheating fluid and a second passage for a fluid to be heated, eachevaporater includ- 9 ing a means for collecting vapor from the fluid inthe second mentioned passage, a pipe lead. lng from the pump outlet tothe first passage of the first calandria, means connecting therespective first passages of the calandrias of the respectiveevaporators in series, means connecting the second passages of therespective calandria of successive evaporators in series for thedelivery of unevaporated liquid sequentially from one to another, meansfor withdrawing from the respecu tive evaporators vapor evaporated fromsuch liquid Iand delivering it to the respective first passages ofsuccessive evaporators, means for disv vchargingl concentrated liquidfrom the second passage of the calandria of 4the last evaporator of theseries, condensing means comprising a heat exchanger having a iiuidpassage adapted to receive vapor and gases from both passages oi a finalevaporator of said series and having a second uid passage adapted toreceive a heat absorbing liquid, means for delivering liquid from thesecond condenser passage to the second passage of the Calandria of thefirst evaporator of said series, and a connection from the first passageof the condenser to the second inlet of said pump whereby vaporsuncondensed in said condenser are re-compressed in said pump by steamfrom said boiler and delivered to the first passage in the calandria ofthe first-evaporator, said pump establishing progressively reducedpressures between the vapor in successive evaporators whereby fluidwhich has caused evaporation in the calandria of one evaporator mayagain cause evaporation in the Calandria of each subsequent evaporator.

' 3. The device of claim 2 in which the first passage of the calandriaof the first evaporator is provided with means for venting uncondensedgas maintained therein under compression by said pump.

d. 'I'he device of claim 2 in which the first passage of the calandriaof the first evaporator is provided with a vent means and said boiler isprovided with a hot well for its water supply with which said vent meanscommunicates below water level.

5. The device of claim 2 in which at least one of said evaporators isprovided with a pre-heater comprising a heat exchanger having `a passagecommunicating with the vapor space of said evaporator to receive vaportherefrom and having another passage connected in series with the secondpassage of the calandria of the first evaporator as an inlet thereto.

6. In a device of the character described, the combination with a steamboiler and a pump having a first inlet connected with the boiler andprovided with a second inlet and an outlet, of rst, second and thirdevaporators each comprising a calandria having a heating fluid passageand a passage for liquid to be heated and a vapor dome, means fordelivering liquid to be heated to the respective calandria passages ofsuccesorator from the preceding evaporator, means for withdrawing thecondensate from the condenser, and a vapor connection from the condenserto the second inlet of said pump whereby vapors uncondensed in saidcondenser are returned by said pump under compression to the heatingpas,- sage of the calandria of the first evaporator.

7. The device of claim 6 in which the heating passage of the calandriaof the rst evaporator is provided with a vent.

8. The device of claim 6 in which the boiler is provided with a hot welland the heating passage of the calandria of the first evaporator isprovided with a vent having a connection to said hot well below thelevel of the boiler therein.

9. The device of claim 6 in which the hot well is provided with meansfor maintaining water therein from said condensate withdrawal means, andwith a pipe leading from said hot Well to the heating fluid passage ofthe calandria of one of said evaporators, the heating fluid passage ofone of said evaporators being vented into said hot well.

l0. A still assembly comprising the combination with a series of stillshaving liquid passages, heating vapor passages and vapor collectingdomes communicating with the liquid passages, oi means connecting thedome of each still with the heating uid passage of a subsequent still,said last mentioned means including a condenser for condensing vaporreceived from such dome, means providing a further connection throughthe same condenser from the heating fluid passage of 'each still to theheating fluid passage' of the subsequent still for delivering condensatefrom the sive evaporators, said means including a pipe heating passagealong with condensate from the dome of each still to the heating fluidpassage of the subsequent still, means connecting the liquid passages ofthe several stills, means for circulating liquid through the severalstills and withdrawing concentrate from the last still of the series,and means for maintaining progressively reducing pressure upon theliquid passages of the respective stills, said means comprising acondenser with which the dome and heating duid passage of the last stillcommunicates, a steam jet compressor having a vapor inlet communicatingwith the condenser toreceive uncondensed gases therefrom, and aconnection from said compressor to the heating passage of the rststill,.said compressor having a steam jet connection whereby steam,vapor, and compressed uncondensed gases are delivered to the heatingfluid passage of the first still' at super-atmospheric pressure, saidpassage of the first still having a vent for such gases, and the dome ofthe last still being maintained at sub-atmospheric pressure.

ll. A still assembly comprising` a plurality of stills and heatexchanger in series, each still comprisingsl heating fluid space, aheated uid space', and a vapor space, and each heat exchanger comprisinga heating iluid space and a heated fluid space, means connecting boththe vapor space il and the heating fluid space of a first still of saidseries to the heating fluid space of' the heat ex changer, means forconnecting the heating fluid space of the said heat exchanger to theheating fluid space of the next successive still of the series, wherebyboth the condensate and vapor and uncondensed heating fluid from theflrst still are led through the heat exchanger to the heating fluidspace of the second still, and means for de livering fluid t be heatedto the heated fluid space of the first still through the heated fluidspace of said heat exchanger.

12.` The assembly of claim 11, further including a connection from theheated fluid space of the first still to the heated fluid space of thesecond still and a return connection for uncondensable gases from afinal still of said series, the means for delivering heating fluid tothe first still of the series including a jet pump for employing theenergy of heating fluid so delivered to recompress the uncondensabiegases returned by .said connection, the heating fluid space of the firststill being provided with a vent for such uncondensable gases.

13. A still assembly comprising a series of stills including at least afirst and a second still, each still including a heating fluid space, aheated fluid space and a vapor space; a heat exchanger between the firstand second stills having a heated fluid space, said exchanger alsohaving a heating fluid space operatively connected between the heatingfluid space of the rst and second stills, a separate connection from thevapor space of the first still to the heating fluid space of saidexchanger, and a connection for delivering fluid from the heated fluidspace of the ilrst still to the heated fluid space of the second; andmeans for delivering heating fluid to the heating fluid space of thefirst still of the series and for removing condensate from the heatingfluid space of the last still of the series, said last means including ajet pump having an inlet connection from the vapor space and the heatingfluid space of the last still of the series, whereby to maintain apressure differential between the successive stills and recompress vaporremoved from the last still for delivery to the rst still, said firststill having a vent opening from its heating Huid space for discharge ofuncondensable gases.

14. In a multiple effect evaporator, each effect comprising a heatingfluid passage, a heated fluid passage and a vapor space, the combinationwith a source of steam under pressure, of `a steam operable compressorhaving a steam inlet, a vapor and gas inlet, and means for dischargingsteam, vapor and gas into the heating fluid space of the first effect,means for venting non-condensable gases from the heating fluid space ofthe first effect, an operative transfer connection from the heatingfluid space and the vapor space of respective effects to the heatingfluid space of successive effects, a condenser provided wlth anoperative connection from the vapor space and the heating fluid space ofthe last mentioned effect and provided with an out-l let in operativeconnection with the vapor and gas inlet of said compressor, saidcompressor comprising means for re-compressing the vapor andnon-condensable gas from the last effect and delivering such vapor andgas under pressure to the heating fluid space of the flrst effect whencesuch gas is vented.

15. The device of claim 14, in which the connections aforesaid fromrespective effects to successive effects include` heat exchange means,and

vhaving a heating fluid passage and a heated fluid passage, each of saidevaporators having a vapor and gas outlet from its heated fluid passageand an outlet 'from its heating fluid passage, a connection from therespective outlets of a first evaporator of said series to the heatingfluid passage of another evaporator of said series, a connection fromthe respective outlets of the last mentioned evaporator to the secondinlet of said compressor for the delivery to the compressor ofuncondensed vapors and uncondensable gases,

and means operatively connecting the compressor outlet with the heatingfluid passage of said flrst evaporator whereby uncondensabie gases fromthe heated fluid passages of the several evaporators are returned to theheating fluid passage of said first evaporator, said compressorestablishing a pressure differential through the evaporators of saidseries and the heating fluid passage of said flrst evaporator being atsuperatmospheric pressure and having a vent for the discharge ofnon-condensable gases accumulated from the passages of the saidevaporators.

17. In a multiple effect evaporator, each effect comprising a heatingfluid space, a heated fluid space and vapor space, the combination withmeans connecting the heated fluid spaces of the several effects insequence for the delivery of heated fluid successively through theseveral effects, of means for venting the heating fluid space of thefirst effect, means for connecting the heating fl-uid space and thevapor spaces of respective effects to the heating fluid spaces ofsuccessive effects, a compressor having a steam, vapor and gas outlet tothe heating fluid space of the flrst effect and having a steam inlet forthe operation of the compressor and an inlet for vapor and gas inoperative connection with the vapor space and the heating fluid spaceofthe last of said successive effects, said compressor comprising meansfor operating the several effects at successively reduced pressures, theheating fluid space of the first effect being at superatmosphericpressures and the heating fluid space of the last of said successiveeffects being at subatmospheric pressures, said compressor alsocomprising means for returning non-condensable gases from the severaleffects to the heating fluid space of the first effect from which s-uchgases are vented by the pressure differential between the heating fluidspace of the first effect and the atmosphere.

18. In combination, a series of evaporators each including a passage forheating fluid and a passage for heated fluid. conduit means connecting rthe heated fluid passages of the several evaporators in series, meansincluding heat exchangers for conducting both heating fluid and vaporfrom respective evaporators to the heating fluid spaces of successiveevaporators, said means being adapted to carry non-condensable gasesfrom the heated fluid passages of the respective evaporators to the lastsuccessive evapdrator aforesaid, means for conducting fluid to be heatedthrough the several heat exchangers sequentially to the heatedfluidpassage of the first evaporator of the series, means for deliveringnoncondensable gases and vapor from the` heating and heated iluidpassages of the last of said successive evaporators to the heating iluidpassage of the rst evaporator at superatmospheric pressure, and meansfor venting the heating fluid passage of said rst evaporator to theatmosphere.

19. The device of claim 18, in which the means for delivering vapor andnon-condensable gases comprises a steam jet compressor arranged todeliver steam from its jet with recompressed va,

pors and gases to the heating fluid passage of said y ilrst evaporator.

20. A method of evaporation which comprises the establishment ofpressure differential between successive stills, passing distilland fromrespective stills to successive stills at successively lower pressure,concurrently passing both heating fluid tive heat exchange relationshipto the distilland in a still previousto such last still, and venting theuncondensaole gases from such previous still.

ROY O. HENSZEY.

raaaaaENoas errati l'The following references are of record in the rileof this patent:

UNITED STATES PATENTS Number Name Date Re. 21,129 Fox June 27, 193921,693 Normandy Oct. 5, 1858 713,298 Goss Nov. 11, 1902 1,213,596DeBaufre Jan. 23, 1917 1,361,834 DeBauIre Dec. 14, 1920 1,387,476DeBauire Aug. 16, 1921 1,390,676 DeBaufre Sept. 13, 1921 1,390,677DeBaufre Sept. 13, 1921 1,706,719 4 Ware Mar. 26, 1929 1,954,371 TarteApr. 10, 1934 2,010,929 Reich Aug. 13, 1935 15 2,104,333 Rosenblad June4, 1938 2,193,483 Hinckley Mar. 12, 1940 FOREIGN PATENTS Number CountryDate 214,273 Great Britain May 28, 1925 OTHER REFERENCES ChemicalEngineers Handbook, Perry, 2nd edition, McGraw-Hill Co., 1941, pages1048, 1049, 1050, 1051, 1052, 1053, 1062-1071, 1072.

Elements of Chemical Engineering Badger & McCabe. 1st edition, 1931,pages 191, 206 to 224. (Copy in Library of Congress.)

Chemical Industry, vol. 43, No. 12, page 302, 1924.

Chemical and Metallurgical Engineering, vol. 28, 1923, pages 26 to 31,73 to 78.

Houghton, Evaporation by the Vapor Compression Method," SelectedEngineering paper No. 7, Institution of Civil Engineers, London 1923, 35pages.

